Technique for linking electrodes together during programming of neurostimulation system

ABSTRACT

An external control device for use with a neurostimulator coupled to a plurality of electrodes capable of conveying electrical stimulation energy into tissue in which the electrodes are implanted. The external control device comprises a user interface including at least one control element, a processor configured for independently assigning stimulation amplitude values to a first set of the electrodes, for linking the first set of electrodes together in response to the actuation of the at least one control element, and for preventing the stimulation amplitude values of the first linked set of electrodes from being varied relative to each other, and output circuitry configured for transmitting the stimulation amplitude values to the neurostimulator.

RELATED APPLICATION DATA

The present application claims the benefit under 35 U.S.C. §119 to U.S.provisional patent application Ser. No. 61/561,760, filed Nov. 18, 2011.The foregoing application is hereby incorporated by reference into thepresent application in its entirety

FIELD OF THE INVENTION

The present inventions relate to tissue stimulation systems, and moreparticularly, to neurostimulation systems for programmingneurostimulation leads.

BACKGROUND OF THE INVENTION

Implantable neurostimulation systems have proven therapeutic in a widevariety of diseases and disorders. Pacemakers and Implantable CardiacDefibrillators (ICDs) have proven highly effective in the treatment of anumber of cardiac conditions (e.g., arrhythmias). Spinal CordStimulation (SCS) systems have long been accepted as a therapeuticmodality for the treatment of chronic pain syndromes, and theapplication of tissue stimulation has begun to expand to additionalapplications such as angina pectoralis and incontinence. Deep BrainStimulation (DBS) has also been applied therapeutically for well over adecade for the treatment of refractory chronic pain syndromes, and DBShas also recently been applied in additional areas such as movementdisorders and epilepsy. Further, in recent investigations, PeripheralNerve Stimulation (PNS) and Peripheral Nerve Field Stimulation (PNFS)systems have demonstrated efficacy in the treatment of chronic painsyndromes and incontinence, and a number of additional applications arecurrently under investigation. Furthermore, Functional ElectricalStimulation (FES) systems, such as the Freehand system by NeuroControl(Cleveland, Ohio), have been applied to restore some functionality toparalyzed extremities in spinal cord injury patients.

These implantable neurostimulation systems typically include one or moreelectrode carrying stimulation leads, which are implanted at the desiredstimulation site, and a neurostimulator (e.g., an implantable pulsegenerator (IPG)) implanted remotely from the stimulation site, butcoupled either directly to the stimulation lead(s) or indirectly to thestimulation lead(s) via a lead extension. The neurostimulation systemmay further comprise an external control device to remotely instruct theneurostimulator to generate electrical stimulation pulses in accordancewith selected stimulation parameters.

Electrical stimulation energy may be delivered from the neurostimulatorto the electrodes in the form of an electrical pulsed waveform. Thus,stimulation energy may be controllably delivered to the electrodes tostimulate neural tissue. The combination of electrodes used to deliverelectrical pulses to the targeted tissue constitutes an electrodecombination, with the electrodes capable of being selectively programmedto act as anodes (positive), cathodes (negative), or left off (zero). Inother words, an electrode combination represents the polarity beingpositive, negative, or zero. Other parameters that may be controlled orvaried include the amplitude, width, and rate of the electrical pulsesprovided through the electrode array. Each electrode combination, alongwith the electrical pulse parameters, can be referred to as a“stimulation parameter set.”

With some neurostimulation systems, and in particular, those withindependently controlled current or voltage sources, the distribution ofthe current to the electrodes (including the case of theneurostimulator, which may act as an electrode) may be varied such thatthe current is supplied via numerous different electrode configurations.In different configurations, the electrodes may provide current orvoltage in different relative percentages of positive and negativecurrent or voltage to create different electrical current distributions(i.e., fractionalized electrode combinations).

As briefly discussed above, an external control device can be used toinstruct the neurostimulator to generate electrical stimulation pulsesin accordance with the selected stimulation parameters. Typically, thestimulation parameters programmed into the neurostimulator can beadjusted by manipulating controls on the external control device tomodify the electrical stimulation provided by the neurostimulator systemto the patient. Thus, in accordance with the stimulation parametersprogrammed by the external control device, electrical pulses can bedelivered from the neurostimulator to the stimulation electrode(s) tostimulate or activate a volume of tissue in accordance with a set ofstimulation parameters and provide the desired efficacious therapy tothe patient. The best stimulus parameter set will typically be one thatdelivers stimulation energy to the volume of tissue that must bestimulated in order to provide the therapeutic benefit (e.g., treatmentof pain), while minimizing the volume of non-target tissue that isstimulated.

However, the number of electrodes available, combined with the abilityto generate a variety of complex stimulation pulses, presents a hugeselection of stimulation parameter sets to the clinician or patient. Forexample, if the neurostimulation system to be programmed has an array ofsixteen electrodes, millions of stimulation parameter sets may beavailable for programming into the neurostimulation system. Today,neurostimulation system may have up to thirty-two electrodes, therebyexponentially increasing the number of stimulation parameters setsavailable for programming.

To facilitate such selection, the clinician generally programs theneurostimulator through a computerized programming system. Thisprogramming system can be a self-contained hardware/software system, orcan be defined predominantly by software running on a standard personalcomputer (PC). The PC or custom hardware may actively control thecharacteristics of the electrical stimulation generated by theneurostimulator to allow the optimum stimulation parameters to bedetermined based on patient feedback or other means and to subsequentlyprogram the neurostimulator with the optimum stimulation parameter setor sets. The computerized programming system may be operated by aclinician attending the patient in several scenarios.

For example, in order to achieve an effective result from SCS, the leador leads must be placed in a location, such that the electricalstimulation will cause paresthesia. The paresthesia induced by thestimulation and perceived by the patient should be located inapproximately the same place in the patient's body as the pain that isthe target of treatment. If a lead is not correctly positioned, it ispossible that the patient will receive little or no benefit from animplanted SCS system. Thus, correct lead placement can mean thedifference between effective and ineffective pain therapy. Whenelectrical leads are implanted within the patient, the computerizedprogramming system, in the context of an operating room (OR) mappingprocedure, may be used to instruct the neurostimulator to applyelectrical stimulation to test placement of the leads and/or electrodes,thereby assuring that the leads and/or electrodes are implanted ineffective locations within the patient.

Once the leads are correctly positioned, a fitting procedure, which maybe referred to as a navigation session, may be performed using thecomputerized programming system to program the external control device,and if applicable the neurostimulator, with a set of stimulationparameters that best addresses the painful site. Thus, the navigationsession may be used to pinpoint the stimulation region or areascorrelating to the pain. Such programming ability is particularlyadvantageous for targeting the tissue during implantation, or afterimplantation should the leads gradually or unexpectedly move that wouldotherwise relocate the stimulation energy away from the target site, orif the pain pattern has worsened or otherwise changed. By reprogrammingthe neurostimulator (typically by independently varying the stimulationenergy on the electrodes), the stimulation region can often be movedback to the effective pain site without having to re-operate on thepatient in order to reposition the lead and its electrode array. Whenadjusting the stimulation region relative to the tissue, it is desirableto make small changes in the proportions of current, so that changes inthe spatial recruitment of nerve fibers will be perceived by the patientas being smooth and continuous and to have incremental targetingcapability.

One known computerized programming system for SCS is called the BionicNavigator®, available from Boston Scientific NeuromodulationCorporation. The Bionic Navigator® is a software package that operateson a suitable PC and allows clinicians to program stimulation parametersinto an external handheld programmer (referred to as a remote control).Each set of stimulation parameters, including fractionalized currentdistribution to the electrodes (as percentage cathodic current,percentage anodic current, or off), may be stored in both the BionicNavigator® and the remote control and combined into a stimulationprogram that can then be used to stimulate multiple regions within thepatient.

Prior to creating the stimulation programs, the Bionic Navigator® may beoperated by a clinician in a “manual programming mode” to manuallyselect the percentage cathodic current and percentage anodic currentflowing through the electrodes, or may be operated by the clinician inan “automated programming mode” to electrically “steer” the currentalong the implanted leads in real-time (e.g., using a joystick orjoystick-like controls), thereby allowing the clinician to determine themost efficacious stimulation parameter sets that can then be stored andeventually combined into stimulation programs. Oftentimes, the BionicNavigator® is operated in the manual programming mode to find a goodstarting electrode combination for the automated programming mode.

Certain computerized programming systems, such as the Bionic Navigator®,are capable of individually and independently varying the amount ofcurrent on each of the electrodes. For example, when programming theneurostimulator in a manual mode, the user may specify the polarity andpercentage of current that flows through any given electrode, asdescribed in U.S. Provisional Patent Application Ser. No. 61/486,141,entitled “Neurostimulation System With On-Effector Programmer Control,”which is expressly incorporated herein by reference. While this featureprovides maximum flexibility when determining the combination ofelectrodes required to achieve optimum therapy, modifying the specifiedamount of current for any given electrode will necessarily modify theamount of current previously specified for other electrodes of the samepolarization, since the total current on the electrodes for the samepolarization must always equal 100 percent.

Despite the seemingly unavoidable consequence of changing the alreadyprogrammed current on other electrodes while specifying the current onanother electrode, oftentimes, there are situations where it isdesirable to maintain a certain electrode combination while adjustingthe current on other electrodes. For example, in the case where thereare multiple target stimulation sites corresponding to, e.g., differentpain regions, it may be desirable to prevent the current valuesoptimally programmed for a particular electrode combination covering oneof the stimulation sites from changing when programming anothercombination of electrodes covering another stimulation site.

Because the perfect electrode combination is needed to provide optimumtherapy when programming a neurostimulator in a manual mode, or to evenserve as a good starting point for programming a neurostimulator in anautomated mode, there thus remains a need to maintain the current valuesprogrammed for any electrode combination when programming otherelectrodes.

SUMMARY OF THE INVENTION

In accordance with the present inventions, an external control device isprovided. The external control device can be used with a neurostimulatorcoupled to a plurality of electrodes capable of conveying electricalstimulation energy into tissue in which the electrodes are implanted.

The external control device comprises a user interface including atleast one control element, and a processor configured for independentlyassigning stimulation amplitude values (e.g., fractionalized electricalcurrent values) to a first set of the electrodes. In one embodiment, theuser interface includes at least another one control element, and theprocessor is configured for independently assigning the stimulationamplitude values to the first set of electrodes in response to actuationof the other control element(s). In another embodiment, the processormay be further configured for designating at least one electrode of thefirst set of electrodes as a cathode and at least another one electrodeof the first set of electrodes as an anode. The external control devicefurther comprises output circuitry configured for transmitting thestimulation amplitude values to the neurostimulator. The externalcontrol device may further comprise a housing containing the userinterface, processor, and output circuitry.

The processor is further configured for linking the first set ofelectrodes together in response to the actuation of the controlelement(s), and for preventing the stimulation amplitude values of thefirst linked set of electrodes from being varied relative to each other.The user interface may further include a display screen configured fordisplaying graphical representations of the electrodes and forgraphically displaying the control elements adjacent the graphicalelectrode representations. In one embodiment, the control elements aresymbols that can be checked, in which case, the processor is configuredfor linking the electrodes associated with the checked symbols. Inanother embodiment, the control elements are the graphical electroderepresentations that can be highlighted, in which case, the processor isconfigured for linking the electrodes associated with the highlightedelectrode representations.

In one embodiment, the processor is configured for locking the firstlinked set of electrodes, such that fractionalized electrical currentvalues of the first linked set of electrodes are prevented from beingvaried when fractionalized electrical current values of a second set ofelectrodes are varied. In this case, the processor may be configured forindependently varying the fractionalized electrical current values ofthe second set of electrodes, such that an amount of fractionalizedelectrical current by which at least one electrode of the second set ofelectrodes is varied is completely compensated for in at least anotherone electrode of the second set of electrodes to conserve one hundredpercent of the total electrical current.

In another embodiment, the processor is configured for globally scalingthe stimulation amplitude values of the first linked set of electrodes.In this case, the processor may be configured for varying fractionalizedelectrical current values of the second set of electrodes in response toglobally scaling fractionalized electrical current values of the firstlinked set of electrodes, such that an amount of fractionalizedelectrical current by which first set of electrodes is globally scaledis completely compensated for in the second set of electrodes toconserve one hundred percent of the total electrical current. Theprocessor may optionally be configured for locking a subset of the firstset of electrodes, such that the fractionalized electrical currentvalues of the subset of electrodes are prevented from being varied whenstimulation amplitude values of the first set of electrodes are globallyscaled.

Other and further aspects and features of the invention will be evidentfrom reading the following detailed description of the preferredembodiments, which are intended to illustrate, not limit, the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The drawings illustrate the design and utility of preferred embodimentsof the present invention, in which similar elements are referred to bycommon reference numerals. In order to better appreciate how theabove-recited and other advantages and objects of the present inventionsare obtained, a more particular description of the present inventionsbriefly described above will be rendered by reference to specificembodiments thereof, which are illustrated in the accompanying drawings.Understanding that these drawings depict only typical embodiments of theinvention and are not therefore to be considered limiting of its scope,the invention will be described and explained with additionalspecificity and detail through the use of the accompanying drawings inwhich:

FIG. 1 is a plan view of a Spinal cord Stimulation (SCS) systemconstructed in accordance with one embodiment of the present inventions;

FIG. 2 is a perspective view of the arrangement of the SCS system ofFIG. 1 with respect to a patient;

FIG. 3 is a profile view of an implantable pulse generator (IPG) andpercutaneous leads used in the SCS system of FIG. 1;

FIG. 4 is front view of a remote control (RC) used in the SCS system ofFIG. 1;

FIG. 5 is a block diagram of the internal components of the RC of FIG.4;

FIG. 6 is a block diagram of the internal components of a clinician'sprogrammer (CP) used in the SCS system of FIG. 1;

FIG. 7 is a plan view of a user interface of the CP of FIG. 6 forprogramming the IPG of FIG. 3;

FIGS. 8 a-8 c are plan views respectively illustrating one method usedby the CP of FIG. 6 to independently lock selected electrodes;

FIGS. 9 a-9 c are plan views respectively illustrating one method usedby the CP of FIG. 6 to lock a set of adjacent electrodes;

FIGS. 10 a-10 c are plan views respectively illustrating one method usedby the CP of FIG. 6 to globally scale a set of adjacent electrodes; and

FIGS. 11 a-11 c are plan views respectively illustrating one method usedby the CP of FIG. 6 to globally scale a set of adjacent electrodes andindependently lock a subset of the adjacent electrodes.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The description that follows relates to a spinal cord stimulation (SCS)system. However, it is to be understood that while the invention lendsitself well to applications in SCS, the invention, in its broadestaspects, may not be so limited. Rather, the invention may be used withany type of implantable electrical circuitry used to stimulate tissue.For example, the present invention may be used as part of a pacemaker, adefibrillator, a cochlear stimulator, a retinal stimulator, a stimulatorconfigured to produce coordinated limb movement, a cortical stimulator,a deep brain stimulator, peripheral nerve stimulator, microstimulator,or in any other neurostimulator configured to treat urinaryincontinence, sleep apnea, shoulder sublaxation, headache, etc.

Turning first to FIG. 1, an exemplary SCS system 10 generally includes aplurality (in this case, two) of implantable neurostimulation leads 12,an implantable pulse generator (IPG) 14, an external remote controllerRC 16, a clinician's programmer (CP) 18, an external trial stimulator(ETS) 20, and an external charger 22.

The IPG 14 is physically connected via one or more percutaneous leadextensions 24 to the neurostimulation leads 12, which carry a pluralityof electrodes 26 arranged in an array. In the illustrated embodiment,the neurostimulation leads 12 are percutaneous leads, and to this end,the electrodes 26 are arranged in-line along the neurostimulation leads12. Alternatively, a surgical paddle lead may be used in place of or inaddition to the percutaneous leads. As will be described in furtherdetail below, the IPG 14 includes pulse generation circuitry thatdelivers electrical stimulation energy in the form of a pulsedelectrical waveform (i.e., a temporal series of electrical pulses) tothe electrode array 26 in accordance with a set of stimulationparameters.

The ETS 20 may also be physically connected via the percutaneous leadextensions 28 and external cable 30 to the neurostimulation leads 12.The ETS 20, which has similar pulse generation circuitry as the IPG 14,also delivers electrical stimulation energy in the form of a pulseelectrical waveform to the electrode array 26 accordance with a set ofstimulation parameters. The major difference between the ETS 20 and theIPG 14 is that the ETS 20 is a non-implantable device that is used on atrial basis after the neurostimulation leads 12 have been implanted andprior to implantation of the IPG 14, to test the responsiveness of thestimulation that is to be provided. Thus, any functions described hereinwith respect to the IPG 14 can likewise be performed with respect to theETS 20. Further details of an exemplary ETS are described in U.S. Pat.No. 6,895,280, which is expressly incorporated herein by reference.

The RC 16 may be used to telemetrically control the ETS 20 via abi-directional RF communications link 32. Once the IPG 14 andneurostimulation leads 12 are implanted, the RC 16 may be used totelemetrically control the IPG 14 via a bi-directional RF communicationslink 34. Such control allows the IPG 14 to be turned on or off and to beprogrammed with different stimulation parameter sets. The IPG 14 mayalso be operated to modify the programmed stimulation parameters toactively control the characteristics of the electrical stimulationenergy output by the IPG 14. As will be described in further detailbelow, the CP 18 provides clinician detailed stimulation parameters forprogramming the IPG 14 and ETS 20 in the operating room and in follow-upsessions.

The CP 18 may perform this function by indirectly communicating with theIPG 14 or ETS 20, through the RC 16, via an IR communications link 36.Alternatively, the CP 18 may directly communicate with the IPG 14 or ETS20 via an RF communications link (not shown). The clinician detailedstimulation parameters provided by the CP 18 are also used to programthe RC 16, so that the stimulation parameters can be subsequentlymodified by operation of the RC 16 in a stand-alone mode (i.e., withoutthe assistance of the CP 18).

The external charger 22 is a portable device used to transcutaneouslycharge the IPG 14 via an inductive link 38. For purposes of brevity, thedetails of the external charger 22 will not be described herein. Detailsof exemplary embodiments of external chargers are disclosed in U.S. Pat.No. 6,895,280, which has been previously incorporated herein byreference. Once the IPG 14 has been programmed, and its power source hasbeen charged by the external charger 22 or otherwise replenished, theIPG 14 may function as programmed without the RC 16 or CP 18 beingpresent.

As shown in FIG. 2, the electrode leads 12 are implanted within thespinal column 42 of a patient 40. The preferred placement of theelectrode leads 12 is adjacent, i.e., resting upon, the spinal cord areato be stimulated. Due to the lack of space near the location where theelectrode leads 12 exit the spinal column 42, the IPG 14 is generallyimplanted in a surgically-made pocket either in the abdomen or above thebuttocks. The IPG 14 may, of course, also be implanted in otherlocations of the patient's body. The lead extensions 24 facilitatelocating the IPG 14 away from the exit point of the electrode leads 12.As there shown, the CP 18 communicates with the IPG 14 via the RC 16.

Referring now to FIG. 3, the external features of the neurostimulationleads 12 and the IPG 14 will be briefly described. One of theneurostimulation leads 12(1) has eight electrodes 26 (labeled E1-E8),and the other neurostimulation lead 12(2) has eight electrodes 26(labeled E9-E16). The actual number and shape of leads and electrodeswill, of course, vary according to the intended application. The IPG 14comprises an outer housing 40 for housing the electronic and othercomponents (described in further detail below), and a connector 42 towhich the proximal ends of the neurostimulation leads 12 mates in amanner that electrically couples the electrodes 26 to the electronicswithin the outer housing 40. The outer housing 40 is composed of anelectrically conductive, biocompatible material, such as titanium, andforms a hermetically sealed compartment wherein the internal electronicsare protected from the body tissue and fluids. In some cases, the outerhousing 40 may serve as an electrode.

The IPG 14 includes a battery and pulse generation circuitry thatdelivers the electrical stimulation energy in the form of a pulsedelectrical waveform to the electrode array 26 in accordance with a setof stimulation parameters programmed into the IPG 14. Such stimulationparameters may comprise electrode combinations, which define theelectrodes that are activated as anodes (positive), cathodes (negative),and turned off (zero), percentage of stimulation energy assigned to eachelectrode (fractionalized electrode combinations), and electrical pulseparameters, which define the pulse amplitude (measured in milliamps orvolts depending on whether the IPG 14 supplies constant current orconstant voltage to the electrode array 26), pulse width (measured inmicroseconds), and pulse rate (measured in pulses per second).

Electrical stimulation will occur between two (or more) activatedelectrodes, one of which may be the IPG case. Simulation energy may betransmitted to the tissue in a monopolar or multipolar (e.g., bipolar,tripolar, etc.) fashion. Monopolar stimulation occurs when a selectedone of the lead electrodes 26 is activated along with the housing 40 ofthe IPG 14, so that stimulation energy is transmitted between theselected electrode 26 and case. Bipolar stimulation occurs when two ofthe lead electrodes 26 are activated as anode and cathode, so thatstimulation energy is transmitted between the selected electrodes 26.For example, electrode E3 on the first lead 12 may be activated as ananode at the same time that electrode E11 on the second lead 12 isactivated as a cathode. Tripolar stimulation occurs when three of thelead electrodes 26 are activated, two as anodes and the remaining one asa cathode, or two as cathodes and the remaining one as an anode. Forexample, electrodes E4 and E5 on the first lead 12 may be activated asanodes at the same time that electrode E12 on the second lead 12 isactivated as a cathode.

In the illustrated embodiment, IPG 14 can individually control themagnitude of electrical current flowing through each of the electrodes.In this case, it is preferred to have a current generator, whereinindividual current-regulated amplitudes from independent current sourcesfor each electrode may be selectively generated. Although this system isoptimal to take advantage of the invention, other stimulators that maybe used with the invention include stimulators having voltage regulatedoutputs. While individually programmable electrode amplitudes areoptimal to achieve fine control, a single output source switched acrosselectrodes may also be used, although with less fine control inprogramming. Mixed current and voltage regulated devices may also beused with the invention. Further details discussing the detailedstructure and function of IPGs are described more fully in U.S. Pat.Nos. 6,516,227 and 6,993,384, which are expressly incorporated herein byreference.

It should be noted that rather than an IPG, the SCS system 10 mayalternatively utilize an implantable receiver-stimulator (not shown)connected to the neurostimulation leads 12. In this case, the powersource, e.g., a battery, for powering the implanted receiver, as well ascontrol circuitry to command the receiver-stimulator, will be containedin an external controller inductively coupled to the receiver-stimulatorvia an electromagnetic link. Data/power signals are transcutaneouslycoupled from a cable-connected transmission coil placed over theimplanted receiver-stimulator. The implanted receiver-stimulatorreceives the signal and generates the stimulation in accordance with thecontrol signals.

Referring now to FIG. 4, one exemplary embodiment of an RC 16 will nowbe described. As previously discussed, the RC 16 is capable ofcommunicating with the IPG 14, CP 18, or ETS 20. The RC 16 comprises ahousing 50, which houses internal componentry (including a printedcircuit board (PCB)), and a lighted display screen 52 and button pad 54carried by the exterior of the housing 50. In the illustratedembodiment, the display screen 52 is a lighted flat panel displayscreen, and the button pad 54 comprises a membrane switch with metaldomes positioned over a flex circuit, and a keypad connector connecteddirectly to a PCB. In an optional embodiment, the display screen 52 hastouch screen capabilities. The button pad 54 includes a multitude ofbuttons 56, 58, 60, and 62, which allow the IPG 14 to be turned ON andOFF, provide for the adjustment or setting of stimulation parameterswithin the IPG 14, and provide for selection between screens.

In the illustrated embodiment, the button 56 serves as an ON/OFF buttonthat can be actuated to turn the IPG 14 ON and OFF. The button 58 servesas a select button that allows the RC 16 to switch between screendisplays and/or parameters. The buttons 60 and 62 serve as up/downbuttons that can be actuated to increment or decrement any ofstimulation parameters of the pulse generated by the IPG 14, includingpulse amplitude, pulse width, and pulse rate. For example, the selectionbutton 58 can be actuated to place the RC 16 in a “Pulse AmplitudeAdjustment Mode,” during which the pulse amplitude can be adjusted viathe up/down buttons 60, 62, a “Pulse Width Adjustment Mode,” duringwhich the pulse width can be adjusted via the up/down buttons 60, 62,and a “Pulse Rate Adjustment Mode,” during which the pulse rate can beadjusted via the up/down buttons 60, 62. Alternatively, dedicatedup/down buttons can be provided for each stimulation parameter. Ratherthan using up/down buttons, any other type of actuator, such as a dial,slider bar, or keypad, can be used to increment or decrement thestimulation parameters. Further details of the functionality andinternal componentry of the RC 16 are disclosed in U.S. Pat. No.6,895,280, which has previously been incorporated herein by reference.

Referring to FIG. 5, the internal components of an exemplary RC 16 willnow be described. The RC 16 generally includes a processor 64 (e.g., amicrocontroller), memory 66 that stores an operating program forexecution by the processor 64, as well as stimulation parameter sets ina navigation table (described below), input/output circuitry, and inparticular, telemetry circuitry 68 for outputting stimulation parametersto the IPG 14 and receiving status information from the IPG 14, andinput/output circuitry 70 for receiving stimulation control signals fromthe button pad 54 and transmitting status information to the displayscreen 52 (shown in FIG. 4). As well as controlling other functions ofthe RC 16, which will not be described herein for purposes of brevity,the processor 64 generates new stimulation parameter sets in response tothe user operation of the button pad 54. These new stimulation parametersets would then be transmitted to the IPG 14 via the telemetry circuitry68. Further details of the functionality and internal componentry of theRC 16 are disclosed in U.S. Pat. No. 6,895,280, which has previouslybeen incorporated herein by reference.

As briefly discussed above, the CP 18 greatly simplifies the programmingof multiple electrode combinations, allowing the user (e.g., thephysician or clinician) to readily determine the desired stimulationparameters to be programmed into the IPG 14, as well as the RC 16. Thus,modification of the stimulation parameters in the programmable memory ofthe IPG 14 after implantation is performed by a user using the CP 18,which can directly communicate with the IPG 14 or indirectly communicatewith the IPG 14 via the RC 16. That is, the CP 18 can be used by theuser to modify operating parameters of the electrode array 26 near thespinal cord.

As shown in FIG. 2, the overall appearance of the CP 18 is that of alaptop personal computer (PC), and in fact, may be implemented using aPC that has been appropriately configured to include adirectional-programming device and programmed to perform the functionsdescribed herein. Thus, the programming methodologies can be performedby executing software instructions contained within the CP 18.Alternatively, such programming methodologies can be performed usingfirmware or hardware. In any event, the CP 18 may actively control thecharacteristics of the electrical stimulation generated by the IPG 14 toallow the optimum stimulation parameters to be determined based onpatient feedback and for subsequently programming the IPG 14 with theoptimum stimulation parameters.

To allow the user to perform these functions, the CP 18 includes a mouse72, a keyboard 74, and a programming display screen 76 housed in ahousing 78. It is to be understood that in addition to, or in lieu of,the mouse 72, other directional programming devices may be used, such asa joystick, a button pad, a group of keyboard arrow keys, a roller balltracking device, and horizontal and vertical rocker-type arm switches.Referring to FIG. 6, the CP 18 further includes detection circuitry 80capable of detecting an actuation event on the display screen 76. Suchactuation event may include placing at least one pointing element (notshown) in proximity to at least one graphical object displayed on thedisplay screen 76, as well as possibly other events involving the pointelement(s), such as moving the pointing element(s) across the screen orclicking or tapping with the pointing element(s), as will be describedin further detail below.

In the preferred embodiments described below, the display screen 76takes the form of a digitizer touch screen, which may either passive oractive. If passive, the detection circuitry 80 recognizes pressure or achange in an electrical current when a passive device, such as a fingeror non-electronic stylus, contacts the screen. If active, the detectioncircuitry 80 recognizes a signal transmitted by an electronic pen orstylus. In either case, the detection circuitry 80 is capable ofdetecting when a physical pointing device (e.g., a finger, anon-electronic stylus, or an electronic stylus) is in close proximity tothe screen, whether it be making physical contact between the pointingdevice and the screen or bringing the pointing device in proximity tothe screen within a predetermined distance, as well as detecting thelocation of the screen in which the physical pointing device is in closeproximity. In some embodiments, the display screen 76 takes the form ofa conventional screen, in which case, the pointing element is not anactual pointing device like a finger or stylus, but rather is a virtualpointing device, such as a cursor controlled by a mouse, joy stick,trackball, etc.

As shown in FIG. 6, the CP 18 generally includes a controller/processor82 (e.g., a central processor unit (CPU)) and memory 84 that stores astimulation programming package 86, which can be executed by thecontroller/controller/processor 82 to allow the user to program the IPG14, and RC 16. The CP 18 further includes output circuitry 88 (e.g., viathe telemetry circuitry of the RC 16) for downloading stimulationparameters to the IPG 14 and RC 16 and for uploading stimulationparameters already stored in the memory 66 of the RC 16, via thetelemetry circuitry 68 of the RC 16. Notably, while thecontroller/processor 82 is shown as a single device, the processingfunctions and controlling functions can be performed by a separatecontroller and processor. Thus, it can be appreciated that thecontrolling functions described below as being performed by the CP 18can be performed by a controller, and the processing functions describedbelow as being performed by the CP 18 can be performed by a processor.

Execution of the programming package 86 by the controller/processor 82provides a multitude of display screens (not shown) that can benavigated through via use of afore-described pointing device. Thesedisplay screens allow the clinician to, among other functions, to selector enter patient profile information (e.g., name, birth date, patientidentification, physician, diagnosis, and address), enter procedureinformation (e.g., programming/follow-up, implant trial system, implantIPG, implant IPG and lead(s), replace IPG, replace IPG and leads,replace or revise leads, explant, etc.), generate a pain map of thepatient, define the configuration and orientation of the leads, initiateand control the electrical stimulation energy output by the leads 12,and select and program the IPG 14 with stimulation parameters in both asurgical setting and a clinical setting. Further details discussing theabove-described CP functions are disclosed in U.S. patent applicationSer. No. 12/501,282, entitled “System and Method for Converting TissueStimulation Programs in a Format Usable by an Electrical CurrentSteering Navigator,” and U.S. patent application Ser. No. 12/614,942,entitled “System and Method for Determining Appropriate Steering Tablesfor Distributing Stimulation Energy Among Multiple NeurostimulationElectrodes,” which are expressly incorporated herein by reference.

Most pertinent to the present inventions, execution of the programmingpackage 86 provides a user interface that allows a user to link selectedelectrodes 26 together during programming of the IPG 14, such thatstimulation amplitude values, and in this case fractionalized currentvalues previously assigned to these electrodes 26, cannot be variedrelative to each other. For example, these electrodes 26 can be lockedsuch that their fractionalized electrical current values are preventedfrom being varied when the fractionalized electrical current values ofother electrodes 26 are varied. As another example, these electrodes 26can be linked, such that their stimulation amplitudes values can beglobally scaled up or down.

Referring now to FIG. 7, an exemplary programming screen 100 generatedby the CP 16 to allow a user to program the IPG 14 will now bedescribed. The programming screen 100 includes various control elementsdescribed below that can be actuated to perform various controlfunctions.

A pointing element may be placed on any of the control elements toperform the actuation event. As described above, in the case of adigitizer touch screen, the pointing element will be an actual pointingelement (e.g., a finger or active or passive stylus) that can be used tophysically tap the screen above the respective graphical control elementor otherwise brought into proximity with respect to the graphicalcontrol element. In the case of a conventional screen, the pointingelement will be a virtual pointing element (e.g., a cursor) that can beused to graphically click on the respective control element.

The programming screen 100 includes an electrode combination control 102having arrows that can be actuated by the user to select one of fourdifferent electrode combinations 1-4. The programming screen 100 furtherincludes a stimulation on/off control 104 that can be alternatelyactuated initiate or cease the delivery of electrical stimulation energyfrom the IPG 14 via the selected electrode combination.

The programming screen 100 further includes various stimulationparameter controls that can be operated by the user to manually adjuststimulation parameters for the selected electrode combination. Inparticular, the programming screen 100 includes a pulse width adjustmentcontrol 106 (expressed in microseconds (μs)), a pulse rate adjustmentcontrol 108 (expressed in Hertz (Hz)), and a pulse amplitude adjustmentcontrol 110 (expressed in milliamperes (mA)). Each control includes afirst arrow that can be actuated to decrease the value of the respectivestimulation parameter and a second arrow that can be actuated toincrease the value of the respective stimulation parameter.

Each of the electrode combinations 1-4 can be created using variouscontrol elements. In particular, the programming screen 100 displaysgraphical representations of the leads 12′ including the electrodes 26′.In the illustrated embodiment, each electrode representation 26′ takesthe form of a closed geometric figure, and in this case a rectangle. Inalternative embodiments, the electrode representations 26′ can take theform of other types of closed geometric figures, such as circles. Theelectrode representations 26′ can be touched with a physical pointingdevice or otherwise clicked with a virtual pointing device multipletimes to switch the corresponding active electrode 26 between a positivepolarity (anode), a negative polarity (cathode), and an off-state. Inessence, the electrode representations 26′ themselves operate as thegraphical control elements, the actuations of which prompt thecontroller/processor 82 to assign the polarities to the selectedelectrodes 26. In alternative embodiments, control elements separatefrom the electrode representations 26′ may be used to change thepolarity of the selected electrodes 26.

. To enable selection between a multipolar configuration and a monopolarconfiguration, the programming screen 100 also includesmultipolar/monopolar stimulation selection control 112, which includescheck boxes that can be alternately actuated by the user to selectivelyprovide multipolar or monopolar stimulation. If a multipolar electrodearrangement is desired, at least one of the electrodes E1-E16 will beselected as an anode (+) and at least one other of the electrodes E1-E16will be selected as a cathode (−). If a monopolar electrode arrangementis desired, none of the electrodes E1-E16 will be selected as an anode(+), and thus, the electrode presentations 26′ can only be clicked totoggle the corresponding electrode 26 between a cathode (−) and off (0).

The programming screen 100 further includes an electrode specificcurrent adjustment control 114 that can be manipulated to independentlyvary stimulation amplitude values for the electrodes E1-E16. Inparticular, for each electrode selected to be activated as either acathode or anode, the clinician can click on the upper arrow of thecontrol 114 to incrementally increase the absolute value of thestimulation amplitude of the selected electrode, and the clinician canclick on the lower arrow of the control 114 to incrementally decreasethe absolute value of the stimulation amplitude of the selectedelectrode. The control 114 also includes an indicator that provides analphanumeric indication of the stimulation amplitude currently assignedto the selected electrode. In an optional embodiment, non-alphanumericindicators, such as different colors, different color luminances,different patterns, different textures, different partially-filledobjects, etc., can be used to indicate the stimulation amplitudecurrently assigned to the selected electrodes, as discussed in U.S.patent application Ser. No. 13/200,629, entitled “NeurostimulationSystem and Method for Graphically Displaying Electrode StimulationValues,” which is expressly incorporated herein by reference.

In the illustrated embodiments, the stimulation amplitude values arefractionalized electrical current values (% current), such that thevalues for each polarization totals to 100. However, in alternativeembodiments, the stimulation amplitude values may be normalized currentor voltage values (e.g., 1-10), absolute current or voltage values(e.g., mA or V), etc. Furthermore, the stimulation amplitude values maybe parameters that are a function of current or voltage, such as charge(current amplitude×pulse width) or charge injected per second (currentamplitude×pulse width×rate (or period)).

In alternative embodiments, a stimulation amplitude adjustment control(not shown) may appear next to the electrode representation 26′ that hasbeen touched or clicked, as described in U.S. patent application Ser.No. 13/200,629, which has been previously incorporated herein byreference, or may be superimposed over the electrode representation 26′that has been touched or clicked, as described in U.S. ProvisionalPatent Application Ser. No. 61/486,141, entitled “NeurostimulationSystem with On-Effector Programmer Control,” which is expresslyincorporated herein by reference.

In alternative embodiments, the programming screen 100 facilitatesautomated current steering; for example, by allowing the user to switchbetween a manual mode using the electrode selection and currentadjustment techniques described above, an electronic trolling(“e-troll”) mode that quickly sweeps the electrode array using a limitednumber of electrode configurations to gradually move a cathode inbipolar stimulation, and a Navigation programming mode that finely tunesand optimizes stimulation coverage for patient comfort using a widenumber of electrode configurations, as described in U.S. ProvisionalPatent Application Ser. No. 61/576,924 (Attorney Docket No.11-00026-01), entitled “Seamless Integration of Different ProgrammingModes for a Neurostimulator Programming System,” which is expresslyincorporated herein by reference. Virtual target poles may be utilizedto steer the current within the electrode array, as described in U.S.Provisional Patent Application Ser. No. 61/452,965, entitled“Neurostimulation System for Defining a Generalized Virtual Multipole,”which is expressly incorporated herein by reference.

As briefly discussed above, selected ones of the electrodes 26 can belinked together, such that the fractionalized electrical current valuespreviously assigned to them via manipulation of the current adjustmentcontrol 114 cannot be varied relative to each other. In the illustratedembodiment, the programming screen 100 includes an electrode lockingcontrol 116 that can be actuated (e.g., touched or clicked) to allowselected electrodes 26 to be locked, thereby preventing thefractionalized electrical values previously assigned to the selectedelectrodes from being subsequently varied. The programming screen 100also includes a global electrode scaling control 118 that can beactuated (e.g., touched or clicked) to allow the fractionalizedelectrical values previously assigned to the selected electrodes 26 tobe globally scaled.

In one embodiment, the actuation of the electrode locking control 116prompts the controller/processor 82 to display graphical controlsymbols, such as boxes, respectively adjacent the electroderepresentations 26′. These symbols can then be checked to prompt thecontroller/processor 82 to link together, and in this case to lock, afirst set of electrodes 26 corresponding to these checked symbols, suchthat fractionalized electrical current values initially assigned tothese electrodes are prevented from being varied when fractionalizedelectrical current values of a second set of electrodes are varied. Inalternative embodiments, the graphical symbols can take the form ofclosed geometric figures other than boxes, such as circles, stars,triangles, etc. With reference now to FIGS. 8 a-8 c, one example ofusing check boxes 120 to lock selected electrodes will be discussed.

As illustrated in FIG. 8 a, electrodes E2, E8, E11, and E14-E16 havebeen initially assigned equalized fractionalized anodic current values,and electrodes E3-E7 and E12-E13 have been initially assigned equalizedfractionized cathodic current values.

As illustrated in FIG. 8 b, the current adjustment control 114 has beenactuated at separate times to independently increase the fractionalizedanodic current for electrode E2 to 45% and to increase thefractionalized cathodic current for electrode E3 to 38%. The amount offractionalized current by which electrodes E2-E3 is varied is completelycompensated for in the remaining active electrodes to conserve 100% ofthe total electrical current. In particular, the fractionalized anodiccurrent for electrode E2 has been changed by 28% (from 17% to 45%),which is compensated for by decreasing the fractionalized anodic currentfor each of electrodes E8, E11, and E14-16 by 5% or 6%, and thefractionalized cathodic current for electrode E3 has been changed by 24%(from 14% to 38%), which is compensated for by decreasing thefractionalized cathodic current for each of electrodes E4-E7 and E12-E13by 4%.

Furthermore, the electrode locking control 116 (shown in FIG. 7) hasbeen actuated to display the check boxes 120 adjacent all the electroderepresentations 26′, with the check boxes 120 adjacent the electroderepresentations associated with electrodes E2-E3 being checked,indicating that electrodes E2-E3 have been locked, such that therespective fractionalized cathodic and anodic current values of 45% and38% are not varied when the fractionalized current values on theremaining unlocked active electrodes are varied, unlocked activeelectrodes are deactivated, and/or previously inactive electrodes areactivated.

For example, as shown in FIG. 8 c, the current adjustment control 114(shown in FIG. 7) has been actuated at separate times to independentlyincrease the fractionalized cathodic current for electrode E7 to 33% andto increase the fractionalized anodic current for electrode E16 to 34%.While maintaining the fractionalized anodic current for electrode E2 at45% and the fractionalized cathodic current for electrode E3 at 38%, theamount of fractionalized current by which electrodes E7 and E16 isvaried is completely compensated for in the remaining active electrodesto conserve 100% of the total electrical current. In particular, thefractionalized cathodic current for electrode E7 has been changed by 22%(from 11% to 33%), which is compensated for by decreasing thefractionalized cathodic current for each of electrodes E4-E6 and E12-E13by 4% or 5%, and the fractionalized anodic current for electrode E16 hasbeen changed by 23% (from 11% to 34%), which is compensated for bydecreasing the fractionalized anodic current for each of electrodes E8,E11, and E14-E15 by 6%.

Furthermore, the check boxes 120 adjacent the electrode representationsassociated with electrodes E7 and E16 are shown as being checked,indicating that electrodes E7 and E16 (in addition to electrodes E2 andE3) have been locked, such that the respective fractionalized cathodicand anodic current values of 33% and 34% are not varied when thefractionalized current values on the remaining unlocked activeelectrodes are varied, unlocked active electrodes are deactivated,and/or previously inactive electrodes are activated. Notably, any of thepreviously checked boxes 120 may be touched or otherwise clicked againto uncheck the check boxes 120, thereby unlocking the electrodesassociated with the electrode representations 26′ adjacent the uncheckedboxes 120, such that fractionalized electrical current values assignedto these electrodes can again be varied.

In an alternative embodiment, rather than using control elements in theform of check boxes to lock electrodes, the actuation of the electrodelocking control 116 prompts the controller/processor 82 to enable agroup of adjacent electrode representations 26′ to be highlighted tolock a first set of electrodes 26 corresponding to the highlightedelectrode representations 26′, such that fractionalized electricalcurrent values initially assigned to these electrodes are prevented frombeing varied when fractionalized electrical current values of a secondset of electrodes are varied. With reference now to FIGS. 9 a-9 c, oneexample of highlighting electrode representations 26′ to lock selectedelectrodes will be discussed.

As illustrated in FIG. 9 a, electrodes E1-E2, E7, and E9-E10 have beeninitially assigned equalized fractionalized cathodic current values, andelectrodes E3, E6, E8, and E11 have been initially assigned equalizedfractionized anodic current values.

As illustrated in FIG. 9 b, the current adjustment control 114 has beenactuated at separate times to independently increase the fractionalizedcathodic current for electrode E7 to 62% and to increase thefractionalized anodic current for each of electrode E6 and E8 to 46%.The amount of fractionalized current by which electrodes E6-E8 is variedis completely compensated for in the remaining active electrodes toconserve 100% of the total electrical current. In particular, thefractionalized cathodic current for electrode E7 has been changed by 42%(from 20% to 62%), which is compensated for by decreasing thefractionalized cathodic current for each of electrodes E1-E2 and E9-E10by 10% or 11%, and the fractionalized anodic current for electrodes E6and E8 in total has been changed by 42% (from 50% to 92%), which iscompensated for by decreasing the fractionalized anodic current for eachof electrodes E3 and E11 by 21%.

Furthermore, the group of adjacent electrodes E6-E8 are highlighted witha box 122, which can be accomplished, e.g., by dragging an actual orvirtual pointing device across the screen to create the box 122. Asingle check box 124 with a check is also displayed adjacent the box122, indicating that electrodes E6-E8 have been locked, such that therespective fractionalized anodic, cathodic, and anodic current values of46%, 62%, and 46% are not varied when the fractionalized current valueson the remaining unlocked active electrodes are varied, unlocked activeelectrodes are deactivated, and/or previously inactive electrodes areactivated. The previously checked box 122 may be touched or otherwiseclicked again to uncheck the box 124, thereby unlinking the electrodesassociated with the electrode representations 26′ previously highlightedby the box 122, such that fractionalized electrical current values forthese electrodes can again be independently varied relative to eachother.

As shown in FIG. 9 c, the current adjustment control 114 has beenactuated at separate times to independently increase the fractionalizedcathodic current for each of electrodes E2 and E10 to 15%. Furthermore,the electrode representation corresponding to electrode E14 has beenactuated to designate the electrode E14 as an anode, and the currentadjustment control 114 has been actuated to initially assign afractionalized anodic current for electrodes E14 to 4%. Whilemaintaining the fractionalized anodic current for electrode E6 at 46%,fractionalized cathodic current for electrode E7 at 62%, and thefractionalized anodic current for electrode E8 at 46%, the amount offractionalized current by which electrodes E2, E10, E14 is varied iscompletely compensated for in the remaining active electrodes toconserve 100% of the total electrical current. In particular, thefractionalized cathodic current for electrodes E2 and E10 has beenchanged by a total of 12% (from 18% to 30%), which is compensated for bydecreasing the fractionalized cathodic current for each of electrodes E1and E9 by 6%, and the fractionalized anodic current for electrode E14has been changed by 4% (from 0% to 4%), which is compensated for bydecreasing the fractionalized anodic current for each of electrodes E3and E11 by 2%.

Referring back to FIG. 7, in one embodiment, actuation of the globalelectrode scaling control 118, like the actuation of the electrodelocking control 116, prompts the controller/processor 82 to enable agroup of adjacent electrode representations 26′ to be highlighted inorder to link the electrodes 26 corresponding to the highlightedelectrode representations 26′. However, in this case, highlighting a setof electrodes does not lock them to prevent varying the fractionalizedelectrical current values initially assigned to these electrodes in anabsolute sense as with the electrode locking control 116. Rather,highlighting these electrodes allows the fractionalized electricalcurrent values of the linked electrodes to be globally scaled (ineffect, the fractionalized electrical current values cannot be variedindependently of each other, but can only be varied in proportion toeach other). With reference now to FIGS. 10 a-10 c, one example ofhighlighting electrode representations 26′ to globally scale electrodeswill be discussed.

As illustrated in FIG. 10 a, fractionalized anodic current values of40%, 30%, and 30% have been initially assigned to electrodes E1, E3, andE8, respectively, and a fractionalized cathodic current value of 50% hasbeen initially assigned to each of electrodes E2 and E16. Furthermore,the global electrode scaling control 118 has been actuated to allow theelectrode representations associated with electrodes E1-E3 to behighlighted with a box 126 (e.g., by dragging an actual or virtualpointing device across the screen to create the box 126), indicatingthat electrodes E1-E3 have been linked, such that the respectivefractionalized anodic, cathodic, and anodic current values of 40%, 50%,and 30% can be globally scaled. The previously checked box 126 may betouched or otherwise clicked again, thereby unlinking the electrodesassociated with the electrode representations 26′ previously highlightedby the box 126, such that fractionalized electrical current values forthese electrodes can again be independently varied relative to eachother.

As shown in FIG. 10 b, the current adjustment control 114 can beactuated one time to globally scale the fractionalized current valuesfor electrodes E1-E3 downward, and in this case, by globally scaling thefractionalized current values down by 40%, so that the fractionalizedanodic current value for electrode E1 is decreased from 40% to 24%, thefractionalized cathodic current value for electrode E2 is decreased from50% to 30%, and the fractionalized anodic current value for electrode E3is decreased from 30% to 18%. As can be appreciated, the ratio ofcurrents between electrodes E1-E3 is maintained. The amount offractionalized current by which electrodes E1-E3 is varied is completelycompensated for in the remaining active electrodes to conserve 100% ofthe total electrical current. In particular, the fractionalized anodiccurrent in total for electrodes E1 and E3 has been changed by 28% (from70% to 42%), which is compensated for by increasing the fractionalizedanodic current for electrode E8 by 28% (from 30% to 58%), and thefractionalized cathodic current for electrode E2 has been changed by 20%(from 50% to 30%), which is compensated for by increasing thefractionalized cathodic current for electrode E16 by 20% (from 50% to70%).

As shown in FIG. 10 c, the current adjustment control 114 can beactuated one time to globally scale the fractionalized current valuesfor electrodes E1-E3 upward, and in this case, by globally scaling thefractionalized current values up by 233% (relative to the state of theelectrodes in FIG. 10 b), so that the fractionalized anodic currentvalue for electrode E1 is increased from 24% to 56%, the fractionalizedcathodic current value for electrode E2 is increased from 30% to 70%,and the fractionalized anodic current value for electrode E3 isincreased from 18% to 42%. Again, the ratio of currents betweenelectrodes E1-E3 is maintained, and the amount of fractionalized currentby which electrodes E1-E3 is varied is completely compensated for in theremaining active electrodes to conserve 100% of the total electricalcurrent. In particular, the fractionalized anodic current in total forelectrodes E1 and E3 has been changed by 56% (from 42% to 98%), which iscompensated for by decreasing the fractionalized anodic current forelectrode E8 by 56% (from 58% to 2%), and the fractionalized cathodiccurrent for electrode E2 has been changed by 40% (from 30% to 70%),which is compensated for by decreasing the fractionalized cathodiccurrent for electrode E16 by 40% (from 70% to 30%).

In an alternative embodiment, rather than highlighting a group ofadjacent electrode representations 26′, control elements in the form ofcheck boxes can be displayed adjacent all the electrode representations26′ upon actuation of the global electrode scaling control 118 much likethat shown in the embodiment in FIGS. 8 a-8 c, except that electrodes 26corresponding to the electrode representations 26′ are not locked, butrather are enabled for global scaling of their fractionalized electricalcurrent values.

In an optional embodiment, symbols in the form of, e.g., boxes, can berespectively displayed respectively adjacent the electroderepresentations 26′ that have been highlighted for global scaling, sothat the corresponding electrodes can be selectively locked or unlocked.That is, the symbols can be checked to lock a subset of electrodeswithin the highlighted group of electrodes, such that fractionalizedelectrical current values initially assigned to this subset ofelectrodes are prevented from being varied when the fractionalizedelectrical current values for the highlighted group of electrodes areglobally scaled.

With reference now to FIGS. 11 a-11 c, one example of highlightingelectrode representations 26′ to globally scale electrodes will bediscussed.

The display of FIG. 11 a is similar to that of FIG. 10 a, with theexception that the highlighting of electrodes E1-E3 with the box 126prompts the display of check boxes 128 adjacent the electroderepresentations 26′ corresponding to electrodes E1-E3. The check box 126adjacent the electrode representation associated with electrode E2 beingchecked, indicating that electrode E2 has been locked, such that thefractionalized cathodic current value of 50% is not varied when thefractionalized current values on the remaining unlocked electrodes inthe highlighted group of electrodes E1-E3 are varied.

As shown in FIG. 11 b, the current adjustment control 114 can beactuated one time to globally scale the fractionalized current valuesfor electrodes E1 and E3 downward, and in this case, by globally scalingthe fractionalized current values by 40%, so that the fractionalizedanodic current value for electrode E1 is decreased from 40% to 24%, andthe fractionalized anodic current value for electrode E3 is decreasedfrom 30% to 18%, similar to that illustrated in FIG. 10 b. However, inthis case, the fractionalized cathodic current for electrode E2 is notvaried when the fractionalized current values on electrodes E1 and E3are globally scaled. The amount of fractionalized current by whichelectrodes E1 and E3 is varied is completely compensated for in theremaining active electrodes to conserve 100% of the total electricalcurrent in the same manner discussed above with respect to FIG. 10 b.Because the fractionalized cathodic current for electrode E2 is notvaried, no compensation is required, and thus, the fractionalizedcathodic current for electrode E16 is not varied.

As shown in FIG. 11 c, the current adjustment control 114 can beactuated one time to globally scale the fractionalized current valuesfor electrodes E1 and E3 upward, and in this case, by globally scalingthe fractionalized current values by 233% (relative to the state of theelectrodes in FIG. 11 b), so that the fractionalized anodic currentvalue for electrode E1 is increased from 24% to 56%, and thefractionalized anodic current value for electrode E3 is decreased from18% to 42%. Again, in this case, the fractionalized cathodic current forelectrode E2 is not varied when the fractionalized current values onelectrodes E1 and E3 are globally scaled. The amount of fractionalizedcurrent by which electrodes E1 and E3 is varied is completelycompensated for in the remaining active electrodes to conserve 100% ofthe total electrical current in the same manner discussed above withrespect to FIG. 10 c. Because the fractionalized cathodic current forelectrode E2 is not varied, no compensation is required, and thus, thefractionalized cathodic current for electrode E16 is not varied.

Although the electrode locking techniques (FIGS. 8 and 9) and the globalscaling techniques (FIGS. 10 and 11) have been described in the contextof manually selecting and adjusting the electrical current on theelectrodes, it should be appreciated that these techniques areapplicable to automated current steering, such that, as electricalcurrent is steered along the electrodes, the linked electrodes areeither locked to a certain current value or globally scaled.

Although the foregoing techniques have been described as beingimplemented in the CP 18, it should be noted that this technique may bealternatively or additionally implemented in the RC 16. Furthermore,although particular embodiments of the present inventions have beenshown and described, it will be understood that it is not intended tolimit the present inventions to the preferred embodiments, and it willbe obvious to those skilled in the art that various changes andmodifications may be made without departing from the spirit and scope ofthe present inventions. Thus, the present inventions are intended tocover alternatives, modifications, and equivalents, which may beincluded within the spirit and scope of the present inventions asdefined by the claims.

What is claimed is:
 1. An external control device for use with a neurostimulator coupled to a plurality of electrodes capable of conveying electrical stimulation energy into tissue in which the electrodes are implanted, comprising: a user interface including at least one control element; a processor configured for independently assigning stimulation amplitude values to a first set of the electrodes, for linking the first set of electrodes together in response to the actuation of the at least one control element, and for preventing the stimulation amplitude values of the first linked set of electrodes from being varied relative to each other; and output circuitry configured for transmitting the stimulation amplitude values to the neurostimulator.
 2. The external control device of claim 1, wherein the user interface includes at least another one control element, and the processor is configured for independently assigning the stimulation amplitude values to the first set of electrodes in response to actuation of the at least other one control element.
 3. The external control device of claim 1, wherein the processor is further configured for designating at least one electrode of the first set of electrodes as a cathode and at least another one electrode of the first set of electrodes as an anode.
 4. The external control device of claim 1, wherein the at least one control element comprises a plurality of control elements respectively associated with the plurality of electrodes.
 5. The external control device of claim 4, wherein the user interface further includes a display screen configured for displaying graphical representations of the electrodes.
 6. The external control device of claim 5, wherein the display screen is configured for graphically displaying the control elements.
 7. The external control device of claim 6, wherein the control elements are graphically displayed adjacent the graphical electrode representations.
 8. The external control device of claim 7, wherein the control elements are symbols that can be checked, and the processor is configured for linking the electrodes associated with the checked symbols.
 9. The external control device of claim 6, wherein the control elements are the graphical electrode representations that can be highlighted, and the processor is configured for linking the electrodes associated with the highlighted electrode representations.
 10. The external control device of claim 1, wherein the stimulation amplitude values are fractionalized electrical current values.
 11. The external control device of claim 10, wherein the processor is further configured for locking the first linked set of electrodes, such that the fractionalized electrical current values of the first linked set of electrodes are prevented from being varied when fractionalized electrical current values of a second set of electrodes are varied.
 12. The external control device of claim 11, wherein the user interface includes at least another one control element, and wherein the processor is configured for independently varying the fractionalized electrical current values of the second set of electrodes in response to actuation of the at least other one control element, such that an amount of fractionalized electrical current by which at least one electrode of the second set of electrodes is varied is completely compensated for in at least another one electrode of the second set of electrodes to conserve one hundred percent of the total electrical current.
 13. The external control device of claim 1, wherein the processor is configured for globally scaling the stimulation amplitude values of the first linked set of electrodes.
 14. The external control device of claim 13, wherein the user interface includes at least another one control element, and the processor is configured for globally scaling the stimulation amplitude values of the first linked set of electrodes in response to actuation of the at least other one control element.
 15. The external control device of claim 14, wherein the stimulation amplitude values are fractionalized electrical current values, and the processor is configured for varying the fractionalized electrical current values of the second set of electrodes in response to globally scaling the fractionalized electrical current values of the first linked set of electrodes, such that an amount of fractionalized electrical current by which first set of electrodes is globally scaled is completely compensated for in the second set of electrodes to conserve one hundred percent of the total electrical current.
 16. The external control device of claim 13, wherein the processor is further configured for locking a subset of the first set of electrodes, such that the fractionalized electrical current values of the subset of electrodes are prevented from being varied when stimulation amplitude values of the first set of electrodes are globally scaled.
 17. The external control device of claim 1, further comprising a housing containing the user interface, processor, and output circuitry. 